Triple bonds structural isomers containing

Triple bonds in side chains of aromatics can be reduced to double bonds or completely saturated. The outcome of such reductions depends on the structure of the acetylene and on the method of reduction. If the triple bond is not conjugated with the benzene ring it can be handled in the same way as in aliphatic acetylenes. In addition, electrochemical reduction in a solution of lithium chloride in methylamine has been used for partial reduction to alkenes trans isomers, where applicable) in 40-51% yields (with 2,5-dihydroaromatic alkenes as by-products) [379]. Aromatic acetylenes with triple bonds conjugated with benzene rings can be hydrogenated over Raney nickel to cis olefins [356], or to alkyl aromatics over rhenium sulfide catalyst [54]. Electroreduction in methylamine containing lithium chloride gives 80% yields of alkyl aromatics [379]. 

The extended polymeric chain structure of [rl c2Clfi] ", reported in Ref. 534, also contains such metal-metal triple bonds. Triple order Tc—Tc bonds were also found at the a and (3 forms of Tc2Cl4(dppe)2 [535], The a isomer 1001 has an eclipsed conformation and a Tc—Tc distance of 2.15(1)A, while the (5 isomer 1002 has a twist angle of 35(2)° and a Tc — Tc distance of 2.117(1) A. These last two isomers were prepared by refluxing Tc2C14(PR3)4 (R3 = Et3, Me2Ph) in toluene with and without an excess of dppe, respectively ... 

Isomers C, D, and E were generated by the program only on the fourth and fifth level from structures F and G. Because the program does not contain any heuristic forbidden systems with a triple bond in the trigonal cycle, this system (in square brackets in the scheme) was also actualized for further generation and served as a precursor of six other potential isomers including structural isomer D (Scheme 9). 

The structures and intereonversion of [Ge,C,H ] , n = 2, 3 speeies, Ge -CH2, HGe -CH, H2Ge+-C, and the singlet and triplet states of the eations Ge -CH, H-Ge+-CH2, have been studied using B3LYP and triple-zeta basis sets. The results suggest that Ge-CH eonnectivities are most stable with isomers containing Ge H bonds likely to be only important at high temperatures. 

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